The present invention relates to attachment devices and, more particularly, to high temperature attachment devices for attaching ceramic to metal parts in a high temperature environment such as, for example, in a jet engine.
The efficiency of jet engines can be increased by increasing the operating temperature of gases therein. Such operating temperature has been limited by the ability of materials to withstand such high temperature. Metals tend to soften, flow and burn as temperatures become higher.
It is well known that certain ceramic materials are capable of withstanding higher temperatures than are metals. Although this desirable property has been known for some time, the use of ceramic materials in jet engines has been limited. High temperature ceramic materials tend to be brittle and thus tend to fracture under mechanical stress. Thus, its use in high load bearing and rotating parts has not been favored.
In some of the highest temperature locations such as, for example, in an afterburner diffuser of a military jet engine, the use of certain stationary ceramic parts would be desirable. However, it has been difficult to attach such stationary ceramic parts to the surrounding metal parts in a way which would provide the necessary cushioning to absorb vibrational shock and differential thermal loading at the points of attachment of the ceramic parts to the surrounding metal structure.
Metal clips for holding the ceramic parts in a truly high temperature environment tend to burn and melt away even when made of high temperature metal. Another possibility includes driving pins into holes formed in the ceramic parts. However, problems have been encountered in the development of satisfactory methods for cushioning the ceramic against damage from transmission of mechanical vibrations through the pin to the ceramic and for preventing damage due to differential thermal loading.